Key Concepts and Features of C++ Programming

Lecture Participation Poll #19 Log onto pollev.com/cse374 Or Text CSE374 to 22333 CSE 374: Intermediate Programming Concepts and Tools Lecture 19: Intro to C++ 1

Administrivia HW4 late turn in locks today Reminder: on Friday I gave everyone 3 more late days CSE 374 AU 20 - KASEY CHAMPION 2

Object Oriented Programming Encapsulation - discrete portions of code keep state and implementation private while providing public interfaces Abstraction - the high level interface is exposed to users without detailing underlying code Inheritance - classes can be derived from other classes allowing for shared code Polymorphism - subclasses implement methods of superclasses to allow for a consistent interface CSE 374 AU 21 - KASEY CHAMPION 3

Meet C++ C++ is a general-purpose programming language created as an extension of the C programming language -Sometimes referred to C with Classes -Includes object-oriented, generic and functional features in addition to facilities for low-level memory manipulation -Designed with a bias towards system programming and embedded, resource-constrained software C is (roughly) a subset of C++, a C program can be compiled as a C++ program -You can still use printf but bad style in ordinary C++ code -Can mix C and C++ idioms if needed to work with existing code, but avoid mixing if you can C++ makes it easy to hide a significant amount of complexity -It s powerful, but really dangerous -Once you mix everything together (templates, operator overloading, method overloading, generics, multiple inheritance), it can get really hard to know what s actually happening! C++ is considered a middle level language -can do both system programming and OOP CSE 374 AU 21 - KASEY CHAMPION 4

Features of C++ Machine independent, but platform dependent - C++ executable is not platform-independent but they are machine independent - ie executable compiled on one windows machine can run on all windows machines but not on Linux machines rich library support - standard built in libraries have data structures and algorithms support - lots of 3rd party libraries Compiled language - does not include modern features like garbage collection, dynamic typing - makes C++ SUPER fast Pointer support and direct memory access - enables direct memory manipulation for low-level programming Object oriented - includes classes, objects, inheritance, polymorphism - namespaces allow for intelligent code grouping strongly typed - specific data types that are not interoperable - allows for both static and dynamic type checking - types checked at either compile or runtime 5

C++ Resources Best place to start: C++ Primer, Lippman, Lajoie, Moo, 5thedition Good Online Source: cplusplus.com Serious C++ programmers should read: - Effective C++, Meyers, 3rdEdition - Best practices for standard C++ -Effective Modern C++,. Meyers, O Reilly - Additional best practices for C++11/C++14 CSE 374 AU 20 - KASEY CHAMPION 6

Basic Differences between C and C++ File names end with *.cc or *.cpp or *.cxx -Still use *.h for header files Use a different compiler: g++ instead of gcc C++ uses C preprocessor but libraries are different -#include <cstdlib> -basically the same as <stdlib.h> CSE 374 AU 21 - KASEY CHAMPION 7

Hello World helloworld.c #include <stdio.h> #include <stdlib.h> // for printf() // for EXIT_SUCCESS int main(int argc, char** argv) { printf("Hello, World!\n"); return EXIT_SUCCESS; } #include <iostream> #include <cstdlib> // for cout, endl // for EXIT_SUCCESS int main(int argc, char** argv) { std::cout << "Hello, World!" << std::endl; return EXIT_SUCCESS; } helloworld.cc CSE 374 AU 20 - KASEY CHAMPION 8

Hello World C++ iostream helloworld.cc #include <iostream> #include <cstdlib> // for cout, endl // for EXIT_SUCCESS int main(int argc, char** argv) { std::cout << "Hello, World!" << std::endl; return EXIT_SUCCESS; } iostream is part of the C++ standard library Note: you don t write .h when you include C++ standard library headers But you dofor local headers (e.g. #include "ll.h") iostream declares stream object instances in the std namespace e.g. std::cin, std::cout, std::cerr CSE 374 AU 20 - KASEY CHAMPION 9

Hello World C++ cstdlib helloworld.cc #include <iostream> #include <cstdlib> // for cout, endl // for EXIT_SUCCESS int main(int argc, char** argv) { std::cout << "Hello, World!" << std::endl; return EXIT_SUCCESS; } cstdlib is the C standard library s stdlib.h Nearly all C standard library functions are available to you For C header foo.h, you should #include <cfoo> We include it here for EXIT_SUCCESS, as usual CSE 374 AU 20 - KASEY CHAMPION 10

Hello World C++ std::cout helloworld.cc std::coutis the cout object instance declared by iostream, living within the std namespace C++ s name for stdout std:coutis an object of class ostream http://www.cplusplus.com/reference/ostream/ostream/ Used to format and write output to the console The entire standard library is in the namespace std #include <iostream> #include <cstdlib> // for cout, endl // for EXIT_SUCCESS int main(int argc, char** argv) { std::cout << "Hello, World!" << std::endl; return EXIT_SUCCESS; } Next, another member function on std::coutis invoked to handle << with RHS std::endl std::endlis a pointer to a manipulator function This manipulator function writes newline ('\n') to the ostreamit is invoked on and then flushes the ostream s buffer This enforces that something is printed to the console at this point CSE 374 AU 20 - KASEY CHAMPION 11

Hello World C++ ostrem helloworld.cc The ostreamclass member functions that handle <<return a reference to themselves When std::cout << "Hello, World!"; is evaluated: A member function of the std::cout object is invoked It buffers the string "Hello, World!" for the console And it returns a reference to std::cout #include <iostream> #include <cstdlib> // for cout, endl // for EXIT_SUCCESS int main(int argc, char** argv) { std::cout << "Hello, World!" << std::endl; return EXIT_SUCCESS; } ostream has many different methods to handle << The functions differ in the type of the right- hand side (RHS) of << e.g. if you do std::cout << "foo"; , then C++ invokes cout s function to handle << with RHS char* CSE 374 AU 20 - KASEY CHAMPION 12

I/O in C++ << is an operatordefined by the C++ language Defined in C as well: usually it bit-shifts integers (in C/C++) C++ allows classes and functions to overload operators! Here, the ostream class overloads << i.e. it defines different member functions (methods) that are invoked when an ostream is the left-hand side of the <<operator Std library include a cout and a cin function Operators >> and << act like shell redirection Operators >> and << take left and right operands and return a stream use namespace std or use std::cout & std::cin using namespace std cout << what is your name ; string name; cin >> name; cout << when were you born? ; int year; cin >> year; CSE 374 AU 20 - KASEY CHAMPION 13

Namespaces Groups code logically namespace foo { int doSomething(int x); } name space bar { int doSomething(int x); } int main() { foo::doSomething(3); bar::doSomething(3); } can reuse names for each namespace Disambiguate with :: syntax Can avoid using the prefix with -using namespace foo -doSomething(3) if you are using a namespace in a header, you must also use the name space in the source code CSE 374 AU 20 - KASEY CHAMPION 14

Cout and Types ostream has many different methods to handle << The functions differ in the type of the right- hand side (RHS) of << e.g. if you do std::cout << "foo"; , then C++ invokes cout s function to handle << with RHS char* C++ distinguishes between objectsand primitive types These include the familiar ones from C: char, short, int, long, float, double, etc. C++ also defines bool as a primitive type (woo-hoo!) Use it! CSE 374 AU 20 - KASEY CHAMPION 15

Refined Hello World C++ s standard library has a std::string class Include the string header to use it Seems to be automatically included in iostreamon CSE Linux environment (C++11) but include it explicitly anyway if you use it http://www.cplusplus.com/reference /string/ #include <iostream> #include <cstdlib> #include <string> // for cout, endl // for EXIT_SUCCESS // for string using namespace std; int main(int argc, char** argv) { string hello("Hello, World!"); cout << hello << endl; return EXIT_SUCCESS; } CSE 374 AU 20 - KASEY CHAMPION 16

Refined Hello World The usingkeyword introduces a namespace (or part of) into the current region using namespace std; names from std:: using std::cout; imports only std::cout (used as cout) #include <iostream> #include <cstdlib> #include <string> // for cout, endl // for EXIT_SUCCESS // for string using namespace std; imports all int main(int argc, char** argv) { string hello("Hello, World!"); cout << hello << endl; return EXIT_SUCCESS; } Benefits of We can now refer to std::string as string, std::cout as cout, and std::endl as endl using namespace std; CSE 374 AU 20 - KASEY CHAMPION 17

Refined Hello World Here we are instantiating a std::string object on the stack (an ordinary local variable) Passing the C string "Hello, World!" to its constructor method hello is deallocated (and its destructor invoked) when main returns #include <iostream> #include <cstdlib> #include <string> // for cout, endl // for EXIT_SUCCESS // for string using namespace std; int main(int argc, char** argv) { string hello("Hello, World!"); cout << hello << endl; return EXIT_SUCCESS; } The C++ string library also overloads the << operator Defines a function (notan object method) that is invoked when the left hand side is ostream and the right hand side is std::string http://www.cplusplus.com/reference/string/string/operator<</ CSE 374 AU 20 - KASEY CHAMPION 18

String Manipulation String Concatenation The string class overloads the + operator Creates and returns a new string that is the concatenation of the left and right String Assignment The string class overloads the = operator Copies the right and replaces the string s contents with it #include <iostream> #include <cstdlib> #include <string> // for cout, endl // for EXIT_SUCCESS // for string using namespace std; int main(int argc, char** argv) { string hello("Hello"); hello = hello + ", World!"; cout << hello << endl; return EXIT_SUCCESS; } This statement is complex! First + creates a string that is the concatenation of hello s current contents and ", World!" Then = creates a copy of the concatenation to store in hello Without the syntactic sugar: hello.operator=(hello.operator+(", World!")); CSE 374 AU 20 - KASEY CHAMPION 19

Const New keyword indicating this thing must not change used for global constants: const int CURRENT_YEAR = 2021; global constants look like global variables, but they are OK stylistically 20

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